Japanese Laid-Open Patent Application Publication No. JP H06-323416 discloses a technique in which the vehicle speed on a downhill is maintained to be constant, or the wheel slip is suppressed by way of engine brake control by a continuously variable transmission. Further, in Japanese Laid-Open Patent Application Publication No. JP 559-073651, engine brake effect is enhanced and burden of brake operation is lessened by causing the speed of the continuously variable transmission from high ratio to low ratio upon detection of the driver's brake operation. As described in these, by controlling the transmission ratio (speed ratio) of the continuously variable transmission (CVT), it is known to impart an engine brake. However, in reality, it is difficult to obtain a smooth deceleration effect, and in particular, controlling at the vehicle stopping operation has been difficult.
On the other hand, in Japanese Laid-Open Patent Application Publication No. JP 2000-065196, a vehicle speed at which the driver's brake operation has been released is stored as a brake release vehicle speed, and when the subsequent vehicle speed becomes higher than the brake release vehicle speed, engine brake will be increased in accordance with the speed deviation and road gradient.
In Japanese Laid-Open Patent Application Publication No. JP 2000-065196 described above, since the engine brake is controlled according to the vehicle speed following the brake release operation of the driver, in such a scene in which the driver presses on the brake pedal progressively as the vehicle approaches the preceding vehicle or the stop line, a positive deceleration control would not be available. Stated another way, the driver by him or herself has to take corrective operation by him- or herself in the form of further depression on brake pedal and the like. Thus, it remains area of improvement in terms of the operational assistance.